It is known to express a polypeptide in the form of a histidine fusion polypeptide. In such a polypeptide, a histidine portion of, e.g., 6-18 successive histidine residues is fused to the C- or N-terminus of the polypeptide. Hence it is possible to isolate the histidine fusion polypeptide by means of a nickel-chelate chromatographic column from the supernatant or cell lysate of the cell expressing it.
However, the above column is expensive. Furthermore, its use costs a lot of time. Therefore, it is not suited for the rapid detection of the expression of a histidine fusion polypeptide. But such a detection is necessary, particularly when it is the objective to screen large numbers of cells.
Thus, it is the object of the present invention to provide means by which the expression of a histidine fusion polypeptide can be detected rapidly.